The invention relates generally to controlling power generation plants, which may include gas turbines, steam turbines and heat recovery steam generators (HRSGs). In particular, the invention relates to model based control systems for power generation plants.
Model based control (MBC) systems are well-known and conventional for controlling power generation plants. For example, MBC systems are used to predict optimal operating control settings for industrial gas turbine engines. The MBC system models the operating engine and generates predicted levels of optimal performance for the engine. The MBC system may model the engine in real-time such that the predicted performance levels correspond to current operating conditions of the engine.
By generating predicted optimal performance levels, the MBC system provides a standard against which to measure the actual performance of a power generation plant. The results of the measurement may be applied in a feedback control loop to adjust the actuators that adjust the control input settings for the plant. By comparing the actual performance of the plant to the performance predicted by the MBC system, adjustments may be made to the actuators, such as fuel flow and inlet guide vane position, to improve the performance of the plant. These adjustments may be made in real time so that the plant is operated optimally.
MBC systems typically drive a power generation plant towards the optimal performance predicted by the model of the plant. The optimal performance of the plant is assumed to be optimal performance predicted by the model.
It may not always case that the model accurately predicts the optimal performance conditions of the power generation plant. The model in a MBC system incorporates certain assumptions and estimates regarding the plant and its current operating condition. To the extent that the assumptions and estimates do not accurately represent the plant, the predicted performance conditions generated by the model may not represent the optimal performance conditions for the power generation plant.
Suboptimal performance of a power generation plant can reduce the fuel consumption of the plant, increase the power generated by the plant, reduce emissions from the plant and reduce wear on the plant. There is a long felt need for control systems that govern power generation plants to achieve their optimal performance.